February 29, 2012

MIT Researchers Explain Mysterious Electron Acceleration

by editor

Researchers from MIT report that they have used a massive computer simulation to explain a mysterious phenomenon detected by space probes.

Jan Egedal, an associate professor of physics at MIT, and colleagues explained the source of aurora-causing high-speed electrons in space in their study published in the February 26 edition of the journal Nature Physics.

The finding could lead to a better ability to predict high-energy electron streams in space that could damage satellites.

The researchers' simulation shows that an active region of Earth's magnetotail is about 1,000 times larger than previously believed.

This means a volume of space energized by these magnetic events is sufficient to explain the large numbers of high-speed electrons detected by a number of spacecraft missions.

The team used one of the world's most advanced supercomputers called Kraken to produce the simulations in their research.

This computer has 112,000 processors and consumes as much electricity as a small town.

Egedal said the MIT researchers used 25,000 of its processors for 11 days to follow the motions of 180 billion simulated particles in space over the course of a magnetic reconnection event.

The simulation was performed using a plasma-physics code developed at Los Alamos National Lab (LANL) that analyzes the evolution of magnetic reconnection.

Egedal explained that as the solar wind stretches Earth's magnetic-field lines, the field stores energy like a rubber band being stretched.

He said when the parallel field lines suddenly reconnect, they release that energy all at once, which is what helps propel electrons back toward Earth to impact the upper atmosphere. This impact is thought to generate the glowing upper-atmosphere plasma known as the aurora.

Egedal said similar phenomena may be taking place in much bigger regions of magnetized plasma in space, such as coronal mass ejections (CME).

He said he hopes in the future that the team will be able to carry out simulations that would apply to CMEs.

"We think we can scale up the simulation” by a hundredfold, he said in a press release.

Michael Brown, a professor of physics at Swarthmore College who was not involved in the study, said the results from the research are very significant to the scientific community.

"I think this picture will gain more and more acceptance, and we have to go beyond” the presently accepted picture of plasmas, he said in a press release.

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Image Caption: An artist's rendition of Earth's magnetosphere. A magnetic tail, or magnetotail, is formed by pressure from the solar wind on a planet's magnetosphere. Credit: NASA